The effect of bilateral glossopharyngeal nerve anaesthesia on swallowing in horses.
Authors: Klebe E A, Holcombe S J, Rosenstein D, Boruta D, Bartner L R, Tessier C
Journal: Equine veterinary journal
Summary
# Editorial Summary: Bilateral Glossopharyngeal Nerve Anaesthesia and Equine Swallowing Despite historical clinical assumptions linking glossopharyngeal nerve dysfunction to dysphagia in horses, Klebe and colleagues investigated whether this nerve is actually essential for normal swallowing mechanics by performing bilateral nerve blocks in six healthy horses and comparing their swallowing patterns before and after anaesthesia using fluoroscopy and endoscopy. Whilst blocked horses demonstrated a trend towards increased tongue movements and prolonged time-to-swallow, neither aspiration nor clinical dysphagia occurred, and no significant alterations in swallowing sequence or function were objectively detected. These findings challenge the long-held assumption that glossopharyngeal nerve dysfunction causes dysphagia, suggesting instead that other neural pathways may provide sufficient compensation for normal swallowing in healthy animals. For practitioners investigating dysphagia cases, this research indicates that glossopharyngeal nerve function should not be reflexively assumed as the primary cause, and that normal swallowing observed during clinical examination cannot be used as diagnostic proof of nerve integrity. A more systematic investigation of alternative neurological and mechanical aetiologies may be warranted when managing dysphagic horses, as the true functional contribution of the glossopharyngeal nerve in pathological conditions remains to be clarified.
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Practical Takeaways
- •Normal swallowing function cannot be used as a diagnostic test for glossopharyngeal nerve integrity in horses
- •Dysphagia in horses should not be automatically attributed to glossopharyngeal nerve dysfunction without further investigation
- •When evaluating dysphagic horses, consider other causes of swallowing dysfunction as the glossopharyngeal nerve may have redundant or compensatory function
Key Findings
- •Bilateral glossopharyngeal nerve anaesthesia produced no evidence of aspiration or dysphagia in 6 normal horses
- •No measurable differences in swallowing sequence or function were detected between blocked and unblocked horses
- •A trend toward increased tongue pushes and time to swallowing was observed in blocked horses, but was not statistically significant
- •Glossopharyngeal nerve function may not be essential for normal swallowing in healthy horses